Minor changes:

- ROI.getArrayRegion makes sure the ROI and image share the same scene
  - Added a few binary operator methods to metaarray 
  - Fixed flowchart/eq.py handling of metaarray objects

flowchart/eq.py

@@ -1,8 +1,12 @@
 # -*- coding: utf-8 -*-
 from numpy import ndarray, bool_
+from metaarray import MetaArray
 
 def eq(a, b):
     """The great missing equivalence function: Guaranteed evaluation to a single bool value."""
+    if a is b:
+        return True
+        
     try:
         e = a==b
     except ValueError:
@@ -18,12 +22,15 @@ def eq(a, b):
         return e
     elif t is bool_:
         return bool(e)
-    elif isinstance(e, ndarray):
+    elif isinstance(e, ndarray) or (hasattr(e, 'implements') and e.implements('MetaArray')):
         try:   ## disaster: if a is an empty array and b is not, then e.all() is True
             if a.shape != b.shape:
                 return False
         except:
             return False
+        if (hasattr(e, 'implements') and e.implements('MetaArray')):
+             return e.asarray().all()
+        else:
             return e.all()
     else:
         raise Exception("== operator returned type %s" % str(type(e)))

graphicsItems/ROI.py

@@ -965,6 +965,8 @@ class ROI(GraphicsObject):
         
         See :func:`getArrayRegion <pyqtgraph.ROI.getArrayRegion>` for more information.
         """
+        if self.scene() is not img.scene():
+            raise Exception("ROI and target item must be members of the same scene.")
         
         shape = self.state['size']
         

metaarray/MetaArray.py

@@ -305,14 +305,37 @@ class MetaArray(object):
             #return lambda *args, **kwargs: MetaArray(getattr(a.view(ndarray), attr)(*args, **kwargs)
         
     def __eq__(self, b):
-        if isinstance(b, MetaArray):
-            b = b.asarray()
-        return self._data == b
+        return self._binop('__eq__', b)
         
     def __ne__(self, b):
+        return self._binop('__ne__', b)
+        #if isinstance(b, MetaArray):
+            #b = b.asarray()
+        #return self.asarray() != b
+        
+    def __sub__(self, b):
+        return self._binop('__sub__', b)
+        #if isinstance(b, MetaArray):
+            #b = b.asarray()
+        #return MetaArray(self.asarray() - b, info=self.infoCopy())
+
+    def __add__(self, b):
+        return self._binop('__add__', b)
+
+    def __mul__(self, b):
+        return self._binop('__mul__', b)
+        
+    def __div__(self, b):
+        return self._binop('__div__', b)
+        
+    def _binop(self, op, b):
         if isinstance(b, MetaArray):
             b = b.asarray()
-        return self._data != b
+        a = self.asarray()
+        c = getattr(a, op)(b)
+        if c.shape != a.shape:
+            raise Exception("Binary operators with MetaArray must return an array of the same shape (this shape is %s, result shape was %s)" % (a.shape, c.shape))
+        return MetaArray(c, info=self.infoCopy())
         
     def asarray(self):
         if isinstance(self._data, np.ndarray):